Energy self-sufficient radiofrequency transmitter

ABSTRACT

The energy self-sufficient radiofrequency transmitter has at least one electromechanical transducer with a rectifier circuit connected downstream and with a voltage converter circuit. A logic circuit configuration is connected to the voltage converter circuit. The logic circuit configuration has a sequence controller a memory in which an identification code is stored. The energy self-sufficient radiofrequency transmitter also has a radiofrequency transmission stage that is connected to the logic circuit configuration and a transmission antenna.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of copending InternationalApplication No. PCT/DE01/01965, filed May 21, 2001, which designated theUnited States and was not published in English.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to an energy self-sufficient radiofrequencytransmitter, the use thereof, and also to a method for the energyself-sufficient transmission of a radiofrequency signal.

Energy self-sufficient systems in which mechanical energy is convertedinto electrical energy using a piezoelectric transducer and thenrectified are known in the prior art. The electrical energy is used todrive simple resonant circuits.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide an energyself-sufficient radiofrequency transmitter and a method for the energyself-sufficient transmission of a radiofrequency signal that enable thecommunication of information to be improved.

With the foregoing and other objects in view there is provided, inaccordance with the invention, an energy self-sufficient radiofrequencytransmitter, including: at least one electromechanical transducer; arectifier circuit connected downstream from the transducer; a voltageconverter circuit; a logic circuit configuration connected to thevoltage converter circuit; a radiofrequency transmission stage connectedto the logic circuit configuration; and at least one transmissionantenna. The logic circuit configuration includes a sequence controllerand a memory for storing an identification code.

In accordance with an added feature of the invention, theelectromechanical transducer includes at least one piezoelectricelement.

In accordance with an additional feature of the invention, thepiezoelectric element is a bending transducer.

In accordance with another feature of the invention, theelectromechanical transducer includes at least one induction coil.

In accordance with a further feature of the invention, the voltageconverter circuit includes an energy storage element.

In accordance with another added feature of the invention, the voltageconverter circuit can be operated in a clocked manner.

In accordance with another additional feature of the invention, there isprovided, at least one capacitor for storing energy. The capacitor isconnected between the rectifier circuit and the voltage regulatingcircuit.

In accordance with a further added feature of the invention, the logiccircuit configuration includes at least one component selected from agroup consisting of at least one microprocessor and an ASIC.

In accordance with a further additional feature of the invention, thereis provided, at least one sensor connected to the logic circuitconfiguration.

In accordance with yet an added feature of the invention, the logiccircuit configuration is embodied using ULP technology.

In accordance with yet an additional feature of the invention, the logiccircuit configuration has clock generator including an LC resonantcircuit or an RC resonant circuit.

In accordance with yet another feature of the invention, theradiofrequency transmission stage is constructed for transmitting aradiofrequency signal having a frequency of greater than 1 MHz.

In accordance with yet a further feature of the invention, theradiofrequency transmission stage is constructed for transmitting aradiofrequency signal having a frequency between 100 MHz and 30 GHz.

In accordance with yet a further added feature of the invention, theradiofrequency signal can have a bandwidth of more than 100 kHz.

In accordance with yet another added feature of the invention, a delaydevice is connected between the logic circuit configuration and thetransmission antenna.

With the foregoing and other objects in view there is provided, inaccordance with the invention, a method for energy self-sufficientlytransmitting a radiofrequency signal. The method includes: using anelectromechanical transducer to convert a mechanical movement into avoltage signal; obtaining a rectified voltage signal by rectifying thevoltage signal; converting the rectified voltage signal to produce avoltage level that is constant at least in sections; after convertingthe rectified signal, using the rectified voltage signal to supplyenergy to at least one logic circuit configuration; using the logiccircuit configuration to communicate at least one identification code toa radiofrequency transmission stage; and using the radiofrequencytransmission stage and a transmission antenna to radiate aradiofrequency signal containing the identification code.

In accordance with an added mode of the invention, the step of using thelogic circuit configuration to communicate the identification code tothe radiofrequency transmission stage includes: reading out theidentification code from a memory of the logic circuit configuration;generating a transmission telegram including the identification code;activating the radiofrequency transmission stage; and modulating aradiofrequency oscillation with the transmission telegram.

In accordance with an additional mode of the invention, the methodincludes providing measurement data obtained from at least one sensor tothe logic circuit configuration; and impressing the measurement data onthe radiofrequency signal.

In accordance with another mode of the invention, the method includesradiating a plurality of radiofrequency signals one after another; eachone of the plurality of the radiofrequency signals having a completeinformation content.

In accordance with a further mode of the invention, the method includesvariably setting a time interval of individual ones of the plurality ofthe radiofrequency signals with respect to one another.

In accordance with a further added mode of the invention, the methodincludes variably setting a frequency of individual ones of theplurality of the radiofrequency signals with respect to one another.

In accordance with a further additional mode of the invention, themethod includes encrypting information of the radiofrequency signal.

In accordance with yet an added mode of the invention, the methodincludes differently encrypting a plurality of radiofrequency signals.

In accordance with yet an additional mode of the invention, the methodincludes radiating the radiofrequency signal in a time-delayed manner.

In accordance with another added mode of the invention, the methodincludes transmitting the radiofrequency signal with a bandwidth greaterthan 100 kHz.

In accordance with another additional mode of the invention, the methodincludes transmitting the radiofrequency signal with a frequency ofgreater than 1 MHz.

In accordance with a further mode of the invention, the method includestransmitting the radiofrequency signal with a frequency of between 100MHz and 30 GHz.

To that end the radiofrequency transmitter has at least oneelectromechanical transducer with a rectifier circuit connecteddownstream and at least one voltage converter circuit. A logic circuitconfiguration is connected to the voltage converter circuit. The logiccircuit configuration includes at least one sequence controller and amemory in which an identification code is stored. A radiofrequencytransmission stage is connected to the logic circuit configuration andis controlled by the logic circuit configuration. The radiofrequencysignals generated by the radiofrequency transmission stage are radiatedby at least one transmission antenna.

An electromechanical transducer is understood to be a general componentin which mechanical energy can be converted into electrical energy, forexample, a piezo-electric, electrostrictive or magnetostrictive elementor an electromagnetic induction coil.

The mechanical energy can be generated, for example, from:

-   -   a manual actuation of a switch, pushbutton or another operating        element;    -   a directed mechanical force action, for example the opening or        closing of windows or doors or stop switches in industrial        installations;    -   a pressure change, for example in liquids or gases; or    -   a vibration, for example, on machines, wheels, vehicles.

The voltage generated by the transducer is rectified by the rectifiercircuit and is then forwarded to a voltage converter. The voltageconverter ensures that a constant voltage can be tapped off at leastover a short period of time. As a result, voltage spikes are avoided,and moreover, the operating reliability is increased.

The connection between the rectifier and the voltage converter can beeffected directly or via a current storage element that is additionallypresent, e.g. a capacitor. When a capacitor is present, by way ofexample, the downstream voltage converter can convert a typicallyexponentially falling charging voltage of the capacitor into a constantvoltage at least for a short time. However, the converter can also storethe electrical voltages itself.

Given the presence of a sufficient voltage signal for supplying energyto the logic circuit configuration, the logic circuit configurationcommunicates at least one identification code, and if appropriate, otherinformation as well, for example sensor measurement signals, to theradio-frequency transmission stage. In the radiofrequency transmissionstage, the voltage signal is used to generate a radiofrequency signalcontaining the identification code and to radiate it via thetransmission antenna.

This method for the energy self-sufficient communication of signals hasthe advantage that the degree of utilization of the energy supplied bythe transducer, with respect to the information density that can beemitted, is very high. Although such a system consumes a higherelectrical energy per unit time compared with simple resonant circuitsit is nonetheless possible to transmit a more than proportionally highinformation density per unit time relative thereto. Altogether, thisresults in a better utilization of the electrical energy made availableby the transducer.

In order to achieve a high efficiency and a compact design, it isadvantageous if the electromechanical transducer contains at least onepiezoelement, in particular a piezoelectric bending transducer.

It is also preferred, e.g. in order to achieve an inexpensiveconstruction, if the electromechanical transducer contains at least oneinduction coil.

In order to ensure a sufficiently long energy supply, it is advantageousif at least one energy storage element, e.g. in the form of a capacitor,for storing current is present between the rectifier circuit and thevoltage converter circuit.

In order to increase the efficiency, it is favorable, moreover, if thevoltage converter circuit is equipped with a further energy storageelement. In particular, this is favorable if the voltage convertercircuit is operated in a clocked manner.

It is additionally favorable if the logic circuit configuration isconnected to at least one sensor. As a result, in addition to theidentification code, measurement data from the at least one sensor canalso be acquired or read out by the logic circuit configuration and themeasurement data can be impressed on the radiofrequency signal.

It is also advantageous if, given a voltage supply over a sufficientlylong time, a plurality of radiofrequency signals with completeinformation content are radiated one after the other, because thisredundancy creates an increased communication reliability.

For increased security against interception, it is advantageous if theinformation of the radiofrequency signal is encrypted, typically by anencryption logic integrated into the logic circuit configuration. As aresult, it is also possible to increase the transmission reliability byinputting individual keys, for example for access control purposes. Inparticular, when transmitting a plurality of radiofrequency signals, itis favorable if each of the radiofrequency signals is encrypteddifferently, e.g. with a different key.

Moreover, in order to suppress a transmission disturbance, it isfavorable if, when transmitting a plurality of radiofrequency signals,their time interval with respect to one another is variable and/or thefrequency of the individual radiofrequency signals differs.

Likewise for the purpose of increased transmission reliability, inparticular in environments with a plurality of radiofrequencytransmitters, it is advantageous if the radiation of the radiofrequencysignal is time-delayed, for example by the variable, e.g. statistical,setting of a delay. The delay can be realized, for example, in thesoftware of the logic circuit configuration. Using radiofrequencytransmitters with in each case a statistically distributed delay time oftheir delay devices makes it possible to increase the transmissionprobability.

In order to reduce the energy consumption of the radiofrequencytransmitter, it is advantageous if the logic circuit configuration isembodied using ultra low power technology (ULP technology).

It is advantageous if the logic circuit configuration contains amicroprocessor or an ASIC (Application-Specific Integrated Circuit)module.

Typically, part of the electrical energy provided by the transducer isused to run up the logic circuit configuration into an operating state.To that end, an oscillating crystal is normally provided as a clockgenerator. For shortening the time for running up the logic circuitconfiguration, it is favorable if, instead of an oscillating crystal, anLC resonant circuit or an RC resonant circuit is present as the clockgenerator.

In order to achieve a high data transmission rate, it is advantageous ifa signal with a frequency of >1 MHz is transmitted using theradiofrequency transmission stage. By way of example, frequencies F ofbetween 100 MHz and 30 GHz are realized in technology nowadays. However,there is no fundamental upper limit for the frequency.

In order to achieve a high data throughput within a short time, it isadvantageous if the bandwidth of the radiofrequency signal is at least100 KHz.

It is preferred if, during a transmission cycle, the logic circuitconfiguration:

-   -   reads out the identification code, for example, from a memory of        the logic circuit configuration;    -   generates a transmission telegram containing at least the        identification code, and if appropriate, other information, for        example, measurement data from sensors;    -   activates the radiofrequency transmission stage; and    -   modulates the transmission telegram onto the radiofrequency        oscillation, and if appropriate, encrypts it and/or subjects it        to a time delay.

The use of the radiofrequency transmitter is particularly advantageousin traffic technology, in particular automotive technology and railtechnology, and/or in building technology, in particular installationtechnology, for example for controlling domestic appliances, electricalinstallations or for access control purposes.

Individual aspects of using the radiofrequency transmitter will now bedescribed in more detail schematically using a mechanically fed lightswitch as an application. It goes without saying, however, that theinvention is not restricted to this specific application.

a) Voltage Generation:

To generate voltage, i.e. to convert mechanical energy into electricalenergy, a piezoelectric bending transducer is used which, e.g. in thecase of a force action of 5 N, experiences a flexure of 5 mm and buildsup a resulting electrical voltage of 50 V across its inherent capacitorof 50 nF. Transducers with these parameters are known in the prior artand match a commercially available light switch well in terms of thedimensions and mechanical requirements.

b) Voltage Conditioning:

Voltage stabilization is obtained by using a prior art voltage converterwith a high efficiency and a high input voltage dynamic range. If thecharging voltage across the capacitor then falls during operation e.g.from 20 V to 5 V, the stabilization circuit provides a constant 3 V atthe output.

c) Energy Consideration:

The following energy consideration is intended to show that it ispossible to operate a processor circuit and a radiofrequency transmitterfor a short time with the energy generated in our exemplary embodiment:

Let the electrical energy in the bending transducer be E=½C·u²=½50·10⁻⁹·50² [V² As/V]=62.5 2 μWs, and approximately 50 μWs thereofremain given 80% efficiency of the transducer. An electronic circuitrequiring e.g. approximately 20 mW (3 V and 6.6 mA) can thus be operatedfor a time duration of t=50 μWs/20 mW=2.5 ms.

d) Transmission Rate and Volume of Data:

If a modulation rate of the radiofrequency transmitter of 100 Kbits/s isassumed, then data with a scope of approximately 250 bits can be emittedin this time. This volume of data suffices for encrypting the identityof the switch and also affords the possibility of increasing thetransmission reliability by repeated emission or the application ofcorrelation methods. Moreover, the use of the logic circuitconfiguration, typically a microprocessor or an ASIC, allows encryptionof the data to be transmitted.

e) Radiofrequency Transmitter:

The radiofrequency transmitter is based on a power of 1 mW, whichsuffices to reliably transmit data to every point within a privateresidence. In this case, a typical scenario is that all the switches,for example light switches, upon actuation, emit one or a plurality ofradiofrequency telegrams which are received by a single receiver and thelatter initiates the corresponding actions (lamp on/off, dimming oflamp, etc.).

It goes without saying that the energy self-sufficient radiofrequencytransmitter is not restricted to an application in building technology,but rather can be used universally. Examples of possible fields ofapplication are switch applications such as manually actuated emergencytransmitters, access authorization interrogations, remote controls,other switches, limit switches in industry, traffic, in privatehouseholds, in meters for water, gas and electricity, as motiondetectors, animal monitoring, break-in/theft protection, and generallyin automotive technology for reducing the wiring harness in motorvehicles, or in railroad systems.

An example of an appropriate sensor system application is a sensor fortemperature, pressure, force and other measurement quantities, inparticular for measuring automobile tire pressure and temperature, axletemperature and accelerations on trains, and the temperature or pressureforce of motors and installations in industry.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin an energy self-sufficient radiofrequency transmitter, it isnevertheless not intended to be limited to the details shown, sincevarious modifications and structural changes may be made therein withoutdeparting from the spirit of the invention and within the scope andrange of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

The sole drawing FIGURE schematically shows the different functionalunits of the radiofrequency transmitter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the sole drawing FIGURE in detail, there is shown anelectromechanical transducer 1, preferably a piezoelectric bendingtransducer or an induction coil that enables mechanical energy to beutilized for charge separation and thus for voltage generation. Themechanical energy originates for example from a mechanical force action,(e.g. button pressing) from a pressure change or a vibration. Thevoltage generated is used to charge a capacitor 7 via a rectifiercircuit 2. Alternatively, direct feeding of the voltage regulatingcircuit 3 is also possible, and by way of example, the transducer 1 canstore the charges itself. The downstream voltage conversion isadvantageous in order to generate, from the exponentially fallingcharging voltage of the capacitor 7, a voltage that is constant over ashort period of time for operating the downstream electronics.

The constant voltage is used to activate and supply the downstream logiccircuit configuration 4 and radiofrequency transmission stage 5 as longas the stored energy permits this. The logic circuit configuration 4contains a microprocessor sequence controller, a memory in which theidentity of the measurement location or of the switch is stored, and(optionally) sensor inputs via which one or a plurality of sensors 8 canbe connected.

If a supply voltage is available due to a mechanical energy feed, thenthe following processor-controlled sequence is initiated:

a) reading-out the identification code;b) reading-out the connected sensors 8 (optional);c) encrypting the data (optional);d) generating a transmission telegram containing the identificationcode;e) activating the radiofrequency transmission stage 5; andf) modulating the radiofrequency oscillation with the transmissiontelegram (optionally a number of times as long as sufficient energy isavailable or until a different termination criterion is reached).

The radiofrequency transmission stage 5 generates a radiofrequencyoscillation that is radiated via the transmission antenna 6. Thetransmission telegram generated by the logic circuit configuration 4 ismodulated onto the oscillation.

1. An energy self-sufficient radiofrequency transmitter, comprising: atleast one electromechanical transducer; a rectifier circuit connecteddownstream from said transducer; a voltage converter circuit; a logiccircuit configuration connected to said voltage converter circuit, saidlogic circuit configuration including a sequence controller and a memoryfor storing an identification code; a radiofrequency transmission stageconnected to said logic circuit configuration; and at least onetransmission antenna.
 2. The energy self-sufficient radiofrequencytransmitter according to claim 1, wherein said electromechanicaltransducer includes at least one piezoelectric element.
 3. The energyself-sufficient radiofrequency transmitter according to claim 2, whereinsaid piezoelectric element is a bending transducer.
 4. The energyself-sufficient radiofrequency transmitter according to claim 1, whereinsaid electromechanical transducer includes at least one induction coil.5. The energy self-sufficient radiofrequency transmitter according toclaim 1, wherein said voltage converter circuit includes an energystorage element.
 6. The energy self-sufficient radiofrequencytransmitter according to claim 5, wherein said voltage converter circuitcan be operated in a clocked manner.
 7. The energy self-sufficientradiofrequency transmitter according to claim 1, comprising at least onecapacitor for storing energy; said capacitor connected between saidrectifier circuit and said voltage regulating circuit.
 8. The energyself-sufficient radiofrequency transmitter according to claim 1, whereinsaid logic circuit configuration includes at least one componentselected from a group consisting of at least one microprocessor and anASIC.
 9. The energy self-sufficient radiofrequency transmitter accordingto claim 1, comprising at least one sensor connected to said logiccircuit configuration.
 10. The energy self-sufficient radiofrequencytransmitter according to claim 1, wherein said logic circuitconfiguration is embodied using ULP technology.
 11. The energyself-sufficient radiofrequency transmitter according to claim 1, whereinsaid logic circuit configuration has clock generator including an LCresonant circuit or an RC resonant circuit.
 12. The energyself-sufficient radiofrequency transmitter according to claim 1, whereinsaid radiofrequency transmission stage is constructed for transmitting aradiofrequency signal having a frequency of greater than 1 MHz.
 13. Theenergy self-sufficient radiofrequency transmitter according to claim 12,wherein said radiofrequency transmission stage is constructed for,transmitting a radiofrequency signal having a frequency between 100 MHzand 30 GHz.
 14. The energy self-sufficient radiofrequency transmitteraccording to claim 12, wherein the radiofrequency signal can have abandwidth of more than 100 kHz.
 15. The energy self-sufficientradiofrequency transmitter according to claim 1, comprising a delaydevice connected between said logic circuit configuration and saidtransmission antenna.
 16. A method for energy self-sufficientlytransmitting a radiofrequency signal, which comprises: using anelectromechanical transducer to convert a mechanical movement into avoltage signal; obtaining a rectified voltage signal by rectifying thevoltage signal; converting the rectified voltage signal to produce avoltage level that is constant at least in sections; after convertingthe rectified signal, using the rectified voltage signal to supplyenergy to at least one logic circuit configuration; using the logiccircuit configuration to communicate at least one identification code toa radiofrequency transmission stage; and using the radiofrequencytransmission stage and a transmission antenna to radiate aradiofrequency signal containing the identification code.
 17. The methodaccording to claim 16, wherein the step of using the logic circuitconfiguration to communicate the identification code to theradiofrequency transmission stage includes: reading out theidentification code from a memory of the logic circuit configuration;generating a transmission telegram including the identification code;activating the radiofrequency transmission stage; and modulating aradiofrequency oscillation with the transmission telegram.
 18. Themethod according to claim 16, which comprises: providing measurementdata obtained from at least one sensor to the logic circuitconfiguration; and impressing the measurement data on the radiofrequencysignal.
 19. The method according to claim 16, which comprises radiatinga plurality of radiofrequency signals one after another; each one of theplurality of the radiofrequency signals having a complete informationcontent.
 20. The method according to claim 19, which comprises variablysetting a time interval of individual ones of the plurality of theradiofrequency signals with respect to one another.
 21. The methodaccording to claim 19, which comprises variably setting a frequency ofindividual ones of the plurality of the radiofrequency signals withrespect to one another.
 22. The method according to claim 16, whichcomprises encrypting information of the radiofrequency signal.
 23. Themethod according to claim 22, which comprises differently encrypting aplurality of radiofrequency signals.
 24. The method according to claim16, which comprises radiating the radiofrequency signal in atime-delayed manner.
 25. The method according to claim 16, whichcomprises transmitting the radiofrequency signal with a bandwidthgreater than 100 kHz.
 26. The method according to claim 16, whichcomprises transmitting the radiofrequency signal with a frequency ofgreater than 1 MHz.
 27. The method according to claim 16, whichcomprises transmitting the radiofrequency signal with a frequency ofbetween 100 MHz and 30 GHz.
 28. A method of using an energyself-sufficient radiofrequency transmitter, which comprises: providingthe energy self-sufficient radiofrequency transmitter with: at least oneelectromechanical transducer, a rectifier circuit connected downstreamfrom said transducer, a voltage converter circuit, a logic circuitconfiguration connected to said voltage converter circuit, said logiccircuit configuration including a sequence controller and a memory forstoring an identification code, a radiofrequency transmission stageconnected to said logic circuit configuration, and at least onetransmission antenna; and using the energy self-sufficientradiofrequency transmitter in a technology selected from a groupconsisting of traffic technology, automotive technology, buildingtechnology, and installation technology.